This invention relates to curing agents for polyepoxides. In one aspect, the invention relates to the curing agents and to methods of making same. In another aspect, the invention relates to cured epoxy resins and to methods of curing polyepoxides using novel curing agents in accordance with the invention. In another aspect, the invention relates to carbon fiber-epoxy resin composites in which the epoxy resin is cured with novel curing agents of the invention.
Epoxy resins form a well known class of resins having outstanding properties for many uses. The resins are made by curing a polyepoxide with a curing agent. Many types of polyepoxides and curing agents are known and are fully described in the literature. While the presently available materials are excellent in their field of use, it is generally advantageous to discover new materials which are useful as alternatives to those presently available provided, of course, that the generally excellent properties of the epoxy resins are retained.
Epoxy resins are widely used in composite materials in which fibers of glass, carbon, and so forth, are impregnated with an epoxy resin system (i.e. a polyepoxide and a curing agent) followed by curing to form the composite product. When carbon fibers are used, one difficulty has arisen in that, if the composite is burned, several of the carbon fibers may be released to the environment and such release can be troublesome. In this regard, it will be noted that carbon fibers are electrically conductive and released fibers may short-circuit or otherwise interfere with electrical components with which it comes in contact.
It is an object of the invention to provide a novel curing agent for polyepoxides. It is a further object to provide a method of curing polyepoxides using a novel curing agent and to provide cured epoxy resins cured therewith. It is still a further object to provide carbon fiber-epoxy resin composites which, upon burning, form a high amount of char which will serve to decrease the release of carbon fibers to the atmosphere.